Diamond which has a band-gap energy of 5.5 eV is inherently a good electric insulator. It is desirable to dope diamond, like Si and Ge, with impurities, thereby introducing either p- or n-type semiconducting characteristics in the diamond.
As a matter of fact, some natural diamonds, although rare, are p-type semiconducting diamonds containing boron and are referred to as type IIb diamond. This type IIb diamond can be synthesized by a super-high pressure process. However, there is no naturally occurring diamond which exhibits the properties of an n-type semiconductor, nor has the synthesis of n-type semiconducting diamond by the super-high pressure process been accomplished.
Type IIb diamonds are described, e.g., in A. S. Vishnevskil, A. G. Gontar, "Electrical conductivity of heavily doped p-type diamond", Sov. Phys. Semicond., vol. 15(6), p. 659 (June 1981); A. S. Vishnevskil, A. G. Gontar, "Electrical conducting of heavily doped p-type diamond", ditto., vol. 11(10) (October 1977); G. N. Bezrukov, L. S. Smirnov, "Some electrical and optical properties of synthetic semiconducting diamonds doped with boron", ditto., vol. 4(4), p. 587 (October 1970); J. J. Hauser, J. R. Patel, "Hopping conductivity in C implanted amorphous diamond, or how to ruin a perfectly good diamond", Solid State Communications, vol. 18, p. 789 (1976); I. G. Austin, R. Wolfe, "Electrical and optical properties of a semiconducting diamond", Proc. Phys. Soc., p.329 (1956); P. T. Wedepohl, "Electrical and optical properties of type IIb diamonds", ditto., p.177 (1957); A. T. Collins, A. W. S. Williams, "The nature of the acceptor centre in semiconducting diamond", J. Phys. C: Solid St. Phys., vol. 4, p.1789 (1971); and V. S. Vavilov, "Ion implantation into diamond", Radiation Effects, vol. 37, p. 229 (1978).
An n-type semiconducting diamond is indispensable to the fabrication of semiconducting diamond devices which depend on a p-n junction for their successful operation. Several attempts have been made to dope diamond with impurities by the super-high pressure synthesis process or ion implantation but none has succeeded in synthesizing an n-type semiconducting diamond having low electrical resistivity and high electron mobility.
The attempts to make an n-type semiconducting diamond are described, e.g., in V. S. Vavilov, E. A. Konorova, "Electric properties of diamond doped by implantation of lithium", Sov. Phys. Semicond., vol. 13(6), p. 635 (1979); V. S. Vavilov, E. A. Konorova, "Conductivity of diamond doped by implantation of phosphorus", ditto., vol. 9(8), p.962 (1976); V. S. Vavilov, E. A. Konorova, "Implantation of antimony ions into diamond", ditto., vol. 6(12), p.1998 (1972); and Jacques C. Bdurgoin, "Study of defects introduced by ion implantation in diamond", J.J.A.P., vol. 14(4), P. 544 (1975).